The invention relates to a spinning pump for melt spinning of polyamides comprising a back plate, a front plate, a central plate with a bore of partially circular cross section for supply of the melt and a bore of partially circular cross section for removing the melt, and a pair of gear wheels.
In melt spinning of polyamide 6.6, the quality of the filaments produced can decrease, in continuous operation, after a certain time. The reason for this has been sought in the melt portion of the system and in the starting polymer. It has now been found that deposits of cracked polyamide 6.6 in the spinning pump can be one of the causes of the reduced quality, which is also expressed in high fluff counts.
Gear pumps for melt spinning of polymer melts are known (European Patent Application EP-A2 0 447 766). The known spinning pumps are connected to a spinning pump block, which serves as a connection between an extruder and the spinning nozzles. The channels of the spinning pump block communicate directly with the bore channels of the spinning pump. In the spinning of nylon, especially in the melt spinning of nylon 6.6, deposits are found in the spinning pump that can make themselves felt over the course of spinning in the form of increasing fluff counts and reduced quality. Known spinning pumps have cylindrical inlet and outlet bores in the central plate, which after relatively long periods of operation exhibit deposits of polymer and products of its decomposition.